Various systems utilize battery backup supply systems, such as uninterruptible power supply (“UPS”) units. The UPS units include batteries that are charged during periods when the system is being powered by an external power source. If the power source is lost, the batteries are used to power the system's load. A typical system may use two different power supplies, one to run the components (such as devices in a server array) and another to charge the batteries. In addition, when the UPS unit is hot swapped, or connected and disconnected from a live power source (such as a DC distribution bus or DC bus), significant mating and demating current potentially cause mechanical failure in the power connectors of the power supply and the UPS unit. In addition, significant inrush current flowing through the batteries may produce high di/dt and dv/dt, disturb the DC bus, and negatively impact the overall system performance.